Cosmic rays and their modulation in the heliosphere by studying gamma rays from the Sun with Fermi-LAT: updated models

The Sun is a known quiescent gamma-ray source. Its gamma-ray steady-state, characterized by two distinct emissions, is unique for its spatially and spectrally distinct components: 1) disc emission due by pion decay of CR hadrons interacting with the solar atmosphere; 2) spatially extended emission from inverse Compton (IC) scattering of CR electrons on the solar photons of the heliosphere. Being produced by CRs, which are affected by solar modulation, the intensity of both emissions is expected to be inversely proportional to the solar activity. After the discovery of the quiet solar emission with EGRET, thanks to the high sensitivity of Fermi-LAT we can now monitor the solar steady-state in the various periods of solar activity. The release of Pass 8 data, with its improved event reconstruction and larger effective area, provides a unique opportunity to refine the study and extend it to different solar activities and also to lower and higher energies. In fact a first study was conducted using 18 month of data during low solar activity, where the best model for IC emission was investigated. Now the recent CR electron and positron measurements by Pamela, AMS-02, Fermi, and the changed solar activity call for a more extended analysis. We present here updates on solar IC models based on available CR measurements for different solar activity.